Sun exposure is unequivocally associated with epidermal (pre)malignancies and with dermal "photoaging". While significant in vivo damage to dermal collagen results from UV-induced stimulation of matrix metalloproteins (MMP), direct interaction of solar UV and dermal collagen is made possible in vivo by the presence of photolabile fluorescent moieties covalently linked to collagen. The latter appear primarily as a result of age-related nonenzymatic processes. Collagen photo-transformations could result in a milieu unfavorable for cell growth and viability by photosensitizing deleterious reactions in situ and/or producing cytotoxic photoproducts. Altered collagen could result in MMP and/or alteration of collagen organization that may change the environment for fibroblast growth. Our specific aims are to (1) Characterize the fluorescent collagen chromophores isolated from dermal type I and type III collagens, (2) Incubate dermal fibroblasts with unirradiated and, if feasible, irradiated product fractions isolated in aim #1 above, (3) Test the ability of extracellular matrix components to modulate the effect of penetrating solar UV wavelengths on dermal fibroblasts in an in vitro model system. We isolate these fluorophores from acid and enzymatic extractions of purified Skh-1 mouse as well as from commercial calf-skin collagen. We will characterize the isolated fluorescent chromophores by absorption and fluorescence spectroscopy, HPLC, fast atom bombardment mass-spectroscopy (FAB-MS), and nuclear magnetic resonance (NMR). We will irradiate the isolated fluorophores with solar wavelengths followed by analysis as before. Fibroblasts will be incubated with added reconstituted photoproduct reaction mixture. We will test fibroblasts for viability, growth, and their dose-response to UV challenge in the presence and absence of added fluorophores. We will carry out dose-response in vitro studies to construct survival curves in the presence and absence of collagen + ground substance proteoglycan and gelatin (denatured collagen). In other experiments, cells will be incubated with pre-irradiated collagen prior to UVA. In addition to providing added insight into photoaging and photocarginogenesis, experiments will assess the effect of dermal-penetrating solar UV wavelengths on the architectural and homeostasis of the resident fibroblasts.